1. Field of the Invention
This invention relates to pumps. More particularly, this invention relates to pumps having one or more collapsible pumping chambers.
2. Description of Prior Art
In U.S. Pat. No. 3,154,021, there is disclosed a pump having three collapsible pumping chambers connected in series. Pumping action is produced by opening, closing or partly closing the three chambers in a particular sequence. In U.S. Pat. No. 2,291,912, U.S. Pat. No. 3,048,121, U.S. Pat. No. 3,148,624 and U.S. Pat. No. 3,175,498, other pumps having one or more collapsible pumping chambers are disclosed, and in U.S. Pat. No. 3,701,618 there is disclosed an extrusion press having collapsible pumping chambers which open and close so as to force extrusion material through a die.